Do You Know How to Calibrate Your Sprayer?

— Written By and last updated by JoAnne Gryder

boom sprayerWith the recent spring weather, many calls have come into the office on how to mix herbicides to suppress or kill those springtime weeds. Most herbicide labels give directions in ounces, pints, quarts or gallons per acre. To correctly apply the right amount of herbicide, one will need to know how many acres you can spray with your particular size sprayer. Listed below is a simple way to calibrate (Boom or Boomless) your sprayer to be certain the amount you are applying per acre.

Boom Sprayer Calibration:

1. Determine nozzle spacing.

2. Refer to the following chart to determine calibration course:

Nozzle Spacing Length of Calibration Course *

                                             

15″ 272′                              28” 146’

18″ 227′                              32” 127’

20″ 204′                              36” 113’

22″ 186′                              40” 102’

24″ 170′

3. Measure and stake off the appropriate calibration course based on nozzle spacing. The course should be on the same type of ground that will be sprayed. (Speeds may be faster on roads than on sod, changing the application rate.)

4. Drive the course in the gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.

5. Park the tractor and maintain the same rpm.

6. Turn on the sprayer and catch the water from one nozzle for exactly the same number of seconds that took to drive the calibration course.

7. Ounces caught = gallons per acre.

8. Check all nozzles. Flow rate should not vary more than 10% among all nozzles. Replace any nozzles that do not fall into this range.

* To determine calibration course for a nozzle spacing not listed, divide 340 by the spacing expressed in feet.

Example Calibration distance for 19-inch nozzle spacing = 340 divided by (19/12) = 215 feet.

Boomless Sprayer Calibration:

1. Measure effective swath width.

2. Refer to the following chart to determine calibration course:

Swath Width Length of Calibration Course *

35′  157′

40′  136′

45′  121′

50′  109′

3. Measure and stake off the appropriate calibration course based on nozzle spacing. The course should be on the same type of ground that will be sprayed. (Speeds may be faster on roads than on sod, changing the application rate.)

4. Drive the course in the gear and rpm you will use when actually spraying. Record the time in seconds. Do this twice and average the time.

5. Park the tractor and maintain the same rpm.

6. Turn on the sprayer and use a trash bag and bucket to catch the water for exactly the same number of seconds that it took to drive the calibration course. (Note: You can also use a 2-liter soda bottle, cut a hole in the side of the bottle, big enough to fit over the cluster nozzle, in place of a trash bag.)

7. Pints caught = gallons per acre.

8. Check all nozzles. Flow rate should not vary more than 10% among all nozzles. Replace any nozzles that do not fall into this range.

* To determine calibration course for a swath width not listed, divide 5460 square feet (1/8 acre) by the swath width in feet. Example Calibration distance for 32- foot swath width = 5460 divided by 32 = 171 feet.

If I can be of assistance please let me know at 336-651-7348.


Missouri Cooperative Extension